Disabling shoulder pain has been documented in persons with complete spinal cord injury (SCI). This also is a significant clinical problem in those patients with incomplete SCI. Weight bearing demands on the shoulder joint from ambulation with an assistive device have been implicated. The goal of this project will be to maximizing walking ability. Specifically, the aims are to define the demands of the shoulder joint by ambulation with forearm crutches and wheeled walkers in persons with incomplete SCI. A second purpose is to relate the identified demands to the patients' lesion level, pattern of upper and lower extremity muscle strength and orthotic support. Four functional groups of SCI subjects (weak/strong, paraplegia/tetraplegia) will be tested. Function of the supraspinatus, infraspinatus, subscapularis, anterior and posterior deltoid, serratus anterior, lower trapezius, sternal pectoralis major, latissimus dorsi and triceps brachii will be recorded with dynamic EMG using intramuscular fine wire electrodes. Motion of the shoulder, elbow, wrist, hip, knee, and ankle will be measured with the VICON Motion Analysis System. Forces exerted on the assistive devices will be recorded with a strain gauge instrumented front wheeled walker and forearm crutches. Lower extremity ground reaction forces will be documented with a force plate. Subjects will ambulate with both assistive devices at a self-selected velocity. Maximal isometric torques for shoulder elevation, shoulder adduction, internal and external rotation; elbow flexion and extension; hip flexion, extension and abduction; knee extension and ankle plantar and dorsiflexion will be measured with a LIDO dynamometer. Maximal forces from the shoulder depressors muscles will be documented with a strain gauge instrumented lever arm. The data will be analyzed to compare stride characteristics, shoulder joint kinematics, kinetics and patterns of muscle activity with the two assistive devices in the four subject groups with repeated measures MANOVA. A criterion level of "safe" assistive device weight bearing force relative to shoulder depressor strength will be determined (based on elevation of the acromion relative to the sternum). The strength and orthotic variables which best predict the assistive device weight bearing forces for a given walking velocity will be determined with step-wise regression analysis. From these algorithms clinicians will be able to predict if patients are exceeding the criterion for "safe" upper extremity weight bearing forces and which device would minimize those forces.